Bearded dragon won't move his right arm

His/Her name is Sunny
I've had him for about a month now & he's been really healthy ever since.
I got him from petco & he didn't look sick and seemed very active and healthy so I chose him.

For the past day he hasn't been climbing his log or his pyramid to bask, and when I woke him up this morning he seemed to want to stay under his log even though he saw the light turn on (he usually waits 1-5 mins and moves onto the sun to bask), he stays on the carpet and doesn't seem to want to move.
When he tries to move he's basically laying on his chest and pushing himself with his back legs while also barely using his left arm, his right arm is the one that he's not using and i checked on it and there's no resistance.

TEMPERATURES:
Left side (Where he sleeps)
75-80
Right Side (Basking)
90-100
Humidity just raised because I had a plate of water in there but it evaporated and the humidity is 50 right now, it's usually in the 20-30s
He eats veggies and only eats crickets when he wants, a little veggies daily but crickets or meal/super worms once every other day. Even thought I feed him crickets/worms everyday sometimes he doesnt want to eat them but i still place them on his bowl and he might eat them overnight. All food has calcium added to it.

Extra info: His eyes still move actively, he react to every fast movement and slowly falls back asleep when he sees me.
Sometimes his eyes are low but i think it's because I woke him up.

I don't know, it's like from one day to another he just stopped using his right arm and barely uses his left, not sure if I hurt him or if he hurt himself, just feel guilty and want to help him
Thanks

Hi there, what exact type of uvb bulb do you have , that's very important. ? Can you post pics of Sunny as well as his set up, also showing the lighting fixtures ? Here's how :
https://www.beardeddragon.org/useruploads/ Then use the XIMG to upload them

If you have a mesh hammock, that may have caused an injury. They get thier nails or toes caught in them while jumping off. If you do have one, just take it down.

He may well have done a serious injury to himself in either an awkward fall or leap that landed badly or if you have a mesh hammock snagged some nails in the mesh and hurt his arm in his panic to get unsnagged.

I recommend you take him to a REPTILE / HERP VET see list here : viewtopic.php?f=45&t=234369&p=1803862&hilit=melissa#p1803862
to have the injured limb examined and xrays taken so you will know exactly what you are dealing with.

If you are lucky it's only a soft-tissue injury (sprain, strain) , but it may be a dislocation or break.

Thank you for your help.
Update: He's still not interested in chasing moving bugs
He's now eating more since I've been assist feeding him everyday
He eats small crickets and small super worms 1-5 daily (dipped in calcium powder + the salad I make him daily
He's now slowly moving both his arms but he still won't do his usual "push-up" & he won't stand on his arms either
He doesn't look sick, his eyes are not low or anything