If the tooth doesn’t hurt you or bother you esthetically, then take a chance and leave it as is. The “fracture” under light your dentist detected is what we called a “craze line fracture” often time this defect is only confined in the outer layer of the tooth (enamel). Often than not, it does nothing to the tooth and it will remain in its size and condition for years. Yes, as a precaution, be proactive and place a crown on it will protect the tooth. But if you don’t want to spend the money or don’t have the money for a crown at this time, leave it as is. Just be informed that if it hurts down the road or if it cracks deeper, you’ll end up with a root canal therapy (RCT) and a crown (double your cost now) in a best case scenario or in the worse case scenario you’ll lose the tooth because the crack is too deep to fix to save the tooth.