Pull out the underwire only a little bit through the hole that it is poking through. Use a tiny piece of duct tape to cover the sharp end of the metal underwire. Push the underwire back through that hole as far as you can.
Use upholstery thread to stich under the hole, all the way up and over it. Tie a knot at the end where you are finished.
Apply some fabric glue over the entire stitched surface, to give the thin material an extra layer of protection. You can also use nail polish instead of the glue.
Isn’t this guide simple and easy to fix your bras? Moreover, it can help you save a lot of money from buying a new bra needlessly.