I fell and hit my knee around the acl area i had no pain when i hit it but the next day the whole knee hurt even around the back side it that normal?

Delayed symptoms.: Sometimes symptoms do not begin until hours after an injury. You likely suffered contusions, sprains, and/or strains in your knee.

Yes. Contusion.: Inflemmtory response to blunt trauma. Apply Ice , Ice and ice. Take Ibuprofen 3/day for a week. Do not exert yourself. This swelling and pain should improve. If Knee becomes unstable or swelling does not get better in a week, get examined by Ortho.