Wrist/forearm tendinitis

I swam a 5-mile open water race last weekend, and about an hour afterward, I began having a lot of pain in my wrist/forearm whenever I move my wrist or thumb. It's been four days, and the pain hasn't improved at all. I tried to swim on it yesterday, but it was too painful so I just kicked. My husband thinks it's tendinitis. Can you get tendinitis from one harder and longer than usual swim? If that's what it is, how long will it take to go away? Should I be doing anything other than ice and ibuprofen? Thanks for your help!