Should I be worried about this?

[stutz]

Squirt has this spot on his plastron.

 

[Bambam1989]

It looks like a rub spot. Is there a spot in his enclosure where he could be struggling to get over. A water or food dish with high sides? Or perhaps a rough rock?
If your not sure we can take a look at a picture of your enclosure and see if we spot any possible causes.
Second opinions are always good.

 

[stutz]

Yeah sometimes when he wants out he keeps try over his water bowl. He likes to try climbing the side and you can hear him thump the bowl.

 

[Bambam1989]

Yeah sometimes when he wants out he keeps try over his water bowl. He likes to try climbing the side and you can hear him thump the bowl.

You may try rearranging the enclosure, and sinking the "bowl" farther into the substrate. What kind of bowl are you using?
If he is trying to climb out of his enclosure it may also be a sign that it is to small.