My joint below my right thumb nail will not bend and when I try to force it it like pops out of place the pain is very bad. Whats wrong/

TRigger FInger. This is a common problem. The tendon that bends the thumb goes through a tunnel and has become swollen. You can try splinting for a while and see if that helps, but, a cortisone injection will make it go away very quickly, see a hand surgeon.