I hit my head on a car now I have a bump on my head and it hurts and I also have this knot on my neck?

Whiplash! With any accident you may end up with broken bones or muscle spasm and tension. Since you are already experiencing some pain and showing signs of head and neck injuries, you need to see a physician or go the er. Don't wait too long, hope you will get better soon. (scdentalimplants, com).
Hematoma. This bump is likely a hematoma and can be observed safely. The neck sound like muslce spasm. Heat, stretching and physical therapy can ehlp your neck pain.