How To Regrow A Broken Nail?

I HAVE ONE FNGERNAIL THAT STOPPED GROWING AFTER WATER HAD BEEN TRAPPED UNDER AN ACRYLIC NAIL FOR A LONG TIME. IT BECAME SORE SO I REMOVED THE ACRYLIC NAIL AND I HAD LOST ABOUT HALF OF THE NAIL. NOW IT HAS STOPPED GROWING. IT HAS BEEN SEVERAL MONTHS NOW. WHAT CAN I DO TO MAKE IT START GROWING AGAIN?