My vein is swollen from the iv when i was in the hospital what should i do?

Should resolve: The vein should slowly shrink on its own.

Warm compresses: Usually warm compresses are enough to reduce swelling. If it does not subside in a few days let it be checked it could be an abscess or a hematoma or thrombophlebitis.

Phlebitis: Can be treated with combination of warm compress and medications such as ibuprofen. Also, if it does nit respond it could be infected and need drainage or/and antibiotics.