The root tip probably hit the bottom of the pot where salts in the soil have accumulated. You can try washing away some of the salts but it’s probably best to repot it or plant it into the ground. If you plan on repotting it or keeping it in a pot long term, you may want to consider root pruning your tree so that the roots won’t circle. By root pruning the tap root, it will encourage lateral branching and your plant will grow better in a pot.
Simon