Yes, you can get your remicade when you have an abscess...they are part of your disease. You need the remicade to get your disease under control and stop these abscesses/fistulas.
I would call your surgeon get this new abscess taken care of asap, and then you can still get your infusion next Thursday.
I have been on remicade for over 5 years, and it has given me my life back. Hang in there.