Depending on the gravity, three weeks might be a little early for some meads. If you didn't check the FG to ensure the mead was done, you may have some dangerously carbonated bottles.
That said, you may have some CO2 remaining in solution even with complete fermentation. If you didn't thoroughly degas you can retain some of that CO2 into the bottle. Not a big deal but maybe not what you intended.
The only way to know for sure would be to test the gravity. If you didn't test before bottling, you may want to sacrifice a bottle, test FG and see if you need to put the mead back into a fermentation vessel to complete fermentation.