I fell while rollerblading and smacked the back of my hand and wrist. I can move it and it has a pretty good bruise. But I can't squeeze or grip because it's weak. Is it broken

We can't tell you if it's broken as we are not there to diagnose it. It could be, it may not be. The only way to know for sure would be to have an x-ray done to it.

send us a copy of the x-ray they do at the ER or at the urgent care facility and we may be able to tell.

but seriously, no way to tell without a x-ray