I went swimming and I was underneath the water I lift up my head and it the concrete hard and I have bump and when I press on it there's a sharp pain?

Expected. to have pain, hope there isn't a wound, if so , you better get seen, and update your tetanus vaccine if your last shot was more than 10 years ago. Otherwise, cold compresses would help right after the trauma, later warm compresses and pain killers, give it time to heal, see your doctor if any other problem, wish you well.
Scalp contusion. The scalp is very well supplied with blood so you can get egg=like bruising. Here is an information sheet on signs of more serious head injury and if any of these are present I recommend urgent assessment at your emergency room or after-hours clinic. https://patient.info/health/head-injury-instructions.