Hi there,
Good to hear that testing is helping you and your abcess is now cleaned up. Your normal bg readings are within NICE guidelines too.
Your wound is still healing even when its clean, the site has to close and it is natural to feel a little run down when recovering from infection or trauma. The antibiotics may have upset your tum. When this happens to me, I have a few spoonfuls of plain probiotic yoghurt to help regain digestive wellness. If you don't like yoghurt, you can buy some probiotic capsules at the chemist, have plenty of fluids whilst your tum is still upset and keep an eye on the abcess site, if it doesn't heal fully go back to the nurse for advice.
I wouldn't worry too much about a slight rise in bg level if I had an infection, it's a sign the body is fighting it. If your bg levels are still rising or go higher after the wound and tum have settled down, why not have a chat with your GP to put your mind at rest.