A good option for a fungal nail treatment at home is to peal and either slice up or grate a potato and apply it to the nail. Wrap it with bit of cling film and leave overnight, best to wear some soaks over it so as to keep it all in place. Then wash it in morning. It somehow seems to draw out the oozy goo of the infection. Potatoes are apparently an anti fungal.
Although if it's an active infection and super painful, it's def needed to go GP and they'll give you an antibiotic.
I've heard of anti fungal nail polish that is supposed to help the discoloration of the nail. Another option, if it's not an active infection and but discolored & problematic, is to go to a chiropodist and ask about getting the nail removed. They can apple a numbing agent and remove it while you are awake, it doesn't take long at all. They can either apply something to the base of the nail bed to make the nail not grow again which is good for if you constantly get infections or they can not do that and just let it grow back. If it grows back it might still be discolored and grow weird.