Ok little question, I have painted my car last Monday and for the first time I made it, I am very happy with the result but on my rear fender with the clear coat on it, you can see some defaults…and no I can’t eliminate those marks just with buffing, I need to sand and repaint

My question is : Do I wait several days to fix it? Or I can fix it now?

Here's my car:

 

Has the paint been baked?
How has the weather been up dere in da nort?
seriously, if the weather hasn't cooperated and the car hasn't been in good temps day and night, the finish could be a little raw yet.
On the other hand, if you've kept it in a heated area, board it down in the problem spot, wetsand it, seal and re-shoot.
I would baby on every coat from the sealer on.. just to be safe.
Somethig else to consider...Where is the bad spot?
You say back fender, You mean the quarter panel?
If so it's not a very friendly spot to just repaint the quarter. especiall if you've spent some time on it and want to keep it nice.
Could be talking re-shoot the entire back end.
edit: Looks great by the way...Nice, clean.