Sulfer smell AFTER fermentation

On 1/23 I brewed a Sierra Nevada pale ale clone. Used US-05 dry yeast. It will be 3 weeks this coming Monday since I brewed. Well, I just happened to knock the fermentation bucket a little earlier and there was a pretty bad smelling sulfur aroma coming out of the airlock. Now I know that a sulfur smell can be pretty normal during fermentation, but all during fermentation I didn’t get any sort of sulfur smell from the airlock at all. Am I just worrying to much or does this seem odd to anyone?

Well, maybe I jumped the gun a bit on this one… Just took the lid off the bucket to take a gravity reading and while you could definitely get some sulfur smell smelling the airlock, it didn’t seem to smell much like sulfur at all with the lid off the bucket.