bug bite and bruising

My 5 yr. old son showed me a bug bite on his testical, with some bruising, last night. So I put some hydrocortizone on it, and told him not to mess with it, and it would go away. But, tonight his bruising has spread over his whole testicle, and it's hurting him. I put some more hydrocortizone on it, and told him to try not to itch it. Has the bruise spread because he was itching it? Should I wait to see if it gets better on it's own, or take him in to his Dr.? Thank you, in advance. mom