I visited a quiet café nestllocated along the Naguri River.

"Nestled" sounds like something is surrounded by something else from all sides, so it's a little strange to say "nestled along [a river]" where the river is only on one side of it. It would be more natural to use the phrase "nestled within" when something is surrounded on all sides. You can still use the word "nestled" in this sentence by saying:

"I visited a quiet cafe nestled within a small area along the Naguri River."

When I stopped by in the morning once before, it was only 10 a.m., yet a group of bikers were already digging into their plates of curry.

The phrase "digging into the curry" can sound like they're eating from the large pot of curry in the kitchen, so I corrected it to be more clear.

Today, since I had already eaten lunch, I just had coffee and managed to hold back but even after I got home, the smell of that curry still wouldn’t leave me. (or: leave my mind)

The curry they serve there is absolutely exquisite, and its mouthwatering aroma lingereds in the air throughout the entire shop.

Be careful when you change verb tenses.

Using present makes the statement a general statement that is not necessarily timebound. That is the first half. The second half is more specific to a moment. If you want to keep it that way, you need to indicate what moment:
"The curry they serve there is absolutely exquisite, and today, the mouthwatering aroma lingered in the air throughout the entire shop."

When I stopped by in thone morning once before, it was only 10 a.m., yet a group of bikers were already digging into the curry.

To make it more concise and simple: "when I stopped by one morning"

Today, since I had already eaten lunch, Iand I had just had coffee and, I managed to hold back b. But even after I got home, the smell of that curry still wouldn’t leave me.

OR "since I had already eaten lunch and just had coffee, ...
I moved your articles around a bit to make it read better. And also, your sentence is getting a bit run-on-y, so I split it into two.

I wondered if the scent had somehow clung to my nose or maybe my brain had been numbed by it.

I agree with the other correction, numb is an odd word choice. I'm not sure what you're trying to describe with this.

The curry they serve there is absolutely exquisite, and its mouthwatering aroma lingereds in the air throughout the entire shop.

Changing tense to be consistent with verb serve

When I stopped by in the morning once before, it was only 10 a.m., yetI saw a group of bikers were already digging into the curry though it was only 10 AM.

Today, since I had already eaten lunch, I just had coffee and managed to hold back, but even after I got home, the smell of that curry still wouldn’t leave me.

I wondered if the scent had somehow clung to my nose or maybe my brain had been numbed by it.

The sentence isn't wrong but I think "numbed by it" doesn't make sense here. I feel like you mean something more along the lines of was obsessed with it?

When I stopped by in the morning once before, it was only 10 a.m., yet a group of bikers were already digging into the curry.

Adding 'when' at the start of the sentence is unnatural here. It's grammatically correct but it sounds strange

Today, since I had already eaten lunch, I just had coffee and managed to hold back but even afteronce I got home, the smell of that curry still wouldn’t leave me.

The word 'after' here is fine but I think the word 'once' better describes what you are trying to convey. This is super minor though so I wouldn't worry about it