Pointer finger hurts to move after playing guitar and piano all day. Should I splint it or just leave it alone?

Rest and ice. Pain in the joint right before the finger tip and can often develop as an overuse tendinitis. This could be seen in repetitive type motions like playing the guitar or piano. Nowadays we see this in people from "texting" over and over. The repetitive motion can micro trauma can lead to tendinitis and possibly arthritis. Rest, ice, and over the counter ibuprofen would be a good place to start.