potentiometer question for a project, please help

Hello, I've built a few simple amps and have used the recommended value pots for them.

But say I had one that required a 1K pot, and I used a 5k or a 1 meg. What are the differences? Thanks.

The difference is 4kΩ or 999kΩ. That's all I can say for sure with the little information you have given.

Whether the different value will work depends entirely how what you are using the pot for. It's like asking if I have a 1 quart bottle, will a 5 quart bottle work. Depends.