Infected dental implant: what to expect?

Hi, I had a dental implant put in place 23 days ago. Went to the dentist 2 days ago and he noticed an infection, in its early stages. To combat it, he prescribed Amoxicillin on 875 milligrams pills every 12 hours. I've taken the pills since Monday and the infection looks worse, like a large pustule. I thought antibiotics would kick in immediatly, but the thing keot growing. Is this a normal development and I should just be patient? Thanks.