I bumped the side of my head very hard getting into my car almost 3 hours ago. slight headache and nausea. hemorrhage or hematoma likely?

Get checked in ER: You are young but you head some headache with nausea. It could be a simple superfical concussion to brain tissue without even any observable imaging defects in ct scan/mri brain. But to be on the safer side , pl. Get yourself checked in the er. They will definitely do a ct scan without contrast dye to r/o bleed-intracranially as you fear, also to r/o brain tissue inj/menigeal tears/blood vs tears.

Bumping the head: No - hemorrhage or hematoma are not very likely in this case. A mild concussion is probably what you are feeling. Both the symptoms you reported are typical of a concussion. Are there any other symptoms?