That is a lousy patch job from a broken valve.
There are brass ones. However the plastic breaking is better than damaging the tank cover it is screwed to.
So near tires, it is better, I think, to let the soft plastic break than damage stuff thrown up by tires.
Bottom line, buy a new valve. Unscrew the old one by removing the two screws and pull out. There wil e a clear hose, clamped to the broken valve. Swap them out and reinstall.
Peace and Blessings..