I have never heard of an association between cellulitis an the odor of blood. That said, the human body is capable of pretty much anything. Also, if it did not start until after you began the antibiotics, that is also a possibility.

I really don't think you need to worry. If you were having all kinds of GI symptoms like belly pain that won't go away, or super duper bad reflux symptoms or any of a whole bunch of other signs and symptoms signifying something more serious, then it might be worth some concern. My money is on the antibiotic, as long as the odor started after or about the same time as you started the abx.