Not sure although I would imagine there could be leftover blood from the surgery. Best to be safe and ask your doctor.
It is possible it could resolve itself so my fingers are crossed for you. What kind of cysts were your others?
The bloating won't go away until the cyst is resolved or removed. Why did they give you antibiotics? Do they feel the cyst burst and are being precautionary? It is not the usual treatment. What is their plan? What size is the cyst? Are they planning surgery?