As has been mentioned, a solitary missed payment will be the credit rating equivalent of a drop in the ocean. You say the "arrears" (for want of a better word) have been cleared now, and your credit report will reflect that next month.
A lot of fuss is made about credit ratings. Unless you're looking to borrow money, or maybe change job, they're irrelevant to you. Think of it like negative equity - that's of no importance at all unless you want to sell your house or borrow against it :-)