Biopsy takes 3-4 days or about 7-10 days depending on the pathologist/center. The tissue is processed, then evaluated by the pathologist who then gives the report.
It is just a precaution for all tissue growth that was removed to test.
Next Steps
Just wait. And by the time your suture are to be removed, you might have your report. (5-7 days I presume)
Health Tips
One problem with mucoceles is that they can recur if you hurt/bite the lip again. Sometimes some gland tissue nearby also gets damaged causing it to recur. Nothing to worry and a small procedure can fix it.