Thank you for your query at DoctorSpring.com
I understand your concern.
Since you just had MRSA infection, the lymph nodes swellings are secondary to the infection and may take some time to completely resolve.
The antibiotic also needs to be reviewed if the swelling is not responding to it.
Regarding the nipple, it is better you get it examined. Although cancer is a remote possibility, the chances of the nipple also being infected is more probable.
So it is better it is examined and if required locally an antibiotic ointment like Mupirocin can be applied to prevent further infection.
Feel free to discuss further,