Can I have Botox while taking erythromycin for a tooth infection?

Yes, you can Have botox while on antibiotics including erythromycin as long as whatever infection you are dealing is not close to where you are being injected with botox. There are no contraindications.

If you have been on antibiotics for a few days already, and the infection is under control, I see no problem with you getting Botox. I personally would not treat close to that area (for example in the jaw muscles or around the mouth) just to be on the safe side.