What Causes Raw Around Anus After Taking Amoxicillin?

I took Amoxicillian last night because my wisdom tooth is causing me problems (erupted at the bottom and irritating the area at the top with no tooth). Now my anus seems kinda raw. Is this a normal side effect? I did not have this problem before I took the medicine and I want to be sure I am not developing an allergy to Amoxicillian because it is so often prescribed.