Decay Under Crown
It does look like decay under your crown. I think you will be best off with a new crown if possible because it will be difficult to fill it nicely as it probably wraps around in between your teeth. Also, some decay may have traveled up underneath your crown. If the decay goes extensively below the gum surface, there is a chance that the tooth may not be repairable and may require an extraction. An x-ray would tell us more. The sooner you have it looked at, the better. Good luck!
Decay or chip?
That area does look like decay developed under your crown. If the decay is not that deep under the crown your dentist may be able to remove the decay and place a restorative filling to patch under the crown. I'd the decay is too deep you would need a new crown. The sooner you have it looked at the better.