I found this on cancer.about.com website. If you are concerned at all, call the doctor's office tomorrow morning. They will be able to tell you if it is a sign of infection.
What to Expect After a LEEP
After a LEEP, you can expect mild
cramping, dark discharge, and possible mild bleeding with discharge. It
is advised to wear a sanitary napkin, but not a tampon.
Most
doctors will advise no sex, douching, tampons, or basically anything in
the vagina for a certain amount of time. Heavy lifting and exercise is
not recommended following a LEEP also.