Definitely cancel! As others have said, you will recover much quicker if you just rest and give your body easy time to fight the cold.
I can just say, that I had a customer on Friday, who had a terrible cold, but I didn't notice until we got down to business. I was really pissed off with him, so inconsiderate! I felt disgusted throughout the booking, and did a whole lot of clock watching, couldn't help myself. I don't kiss, bus still...I literally wanted to throw up when he was licking my nipples, dribbling all over, because he had a blocked nose. Yuccckkk! After he'd finished I jumped straight into a shower and I scrubbed myself for a good 15 mins.
Definitely won't be seeing him again, and your potential customers might make the same decision not to see you again, if you welcome them with a bad cold, and you will loose in the long run.