Thanks for writing your query..
After reading your post, it seems that the lump you are having on your forearm can be an abscess
You should get it examined clinically.
If your doctor after examination, thinks that it needs incision and drainage
, you should get it drained under aseptic conditions.
You should also get the culture/senstivity of the pus discharge done to knoow the causative organism and the antibiotic suitable for the infective organism.
I hope this is helpful to you.