Sounds like it Could be cellulitis lovey.? Its a bacterial infection caused from trauma usually like an insect bite or a wound and usually for example. But there’s also not always a cause for it. It causes redness and inflammation around the limb and can track up and down the site. You may have just been bitten and haven’t realised ? Either way get to the dr as soon as you can. Is it on the side you had your breast cancer?. Could be lymphodema also if it’s on your affected side. I just read your second post.....so does it have a pimple like appearance to it now too .? As you said it might be an abcess.? Either way get it checked lovey. Xxx