Question about handicapped sticker. ?

I'm 24 and just got a temporary handicapped sticker (for 6 months) b/c I've had 3 knee surgeries in a year, just had an ACL replacement a month ago and have a chronic pain condition in my knee. This may sound silly, but there are no 'degrees of the handicapped sticker??' right? I'm afraid that some person that's in a wheelchair is going to drive up right after I park and is going to get me in trouble b/c I took the last parkin... But I legally have every right to be there; correct?