My 2 Year Old On Had To Have Blood Drawn

My 2 year old on had to have blood drawn today and the nurse really did a number I. His arm. She finally had 2 more nurses hold my son down to prick him again. He screamed bloody murder while she drew the blood and now he has a huge blue lump where she first pricked. It's berry tender and swollen. What can I do to help take the lump and swelling down and does he need to have it looked at by the doctor?