Suggest Treatment For Large Red Area Where The Spider Bite Occurred

I believe I was bitten by a spider on Wed. night. It felt like a pin prick for appx. 12 hours combined with two very tiny red dots. Thursday it looked as if it was going to be over. However, since Friday I have a large (fifty cent piece size) red area where the 'bite' occurred, with three small bumps. The bumps are red, are NOT pus filled. The area feels as if I have a bad sunburn. Not sure if I need to do anything, as it is merely uncomfortable. Just doesn't seem to be going away. Thanks!