Inflamed scratch from a biking accident, redness, swelling, and itchy - what should i do?

It depends on the date/time since injury. Acute inflammation typically settles down in one week. If you have worsening redness and or swelling, that implies continued inflammation. In the latter instance you may have possible infection at the injured site. A visit to your doctor for further evaluation is recommended unless the redness and swelling are improving daily from now on.

If the changes mentioned are taking place few days after the accident, a wound infection has to be ruled out. Either your doc or an Urgent Care.