You shouldn't kiss someone when you have a cold sore since cold sores are caused by the herpes virus and you could spread the herpes virus to the person you kiss.
To get rid of the cold sore try applying some baby orajel to the cold sore as it will help to numb the cold sore and make it less painful to eat and will get rid of the cold sore in 2 to 3 days.
Wait until after your cold sore goes away before kissing someone.