As long as the string is in good shape, no need to replace it; adding some twists to the string will shorten the string, thereby increase your brace height.
Unstring your bow taking the top loop only off of the limb (could use the bottom as well, no matter) Once you have the string off of the limb, look down it's long axis and determine which direction you need to twist it to "tighten" it. Put a full 360 degree twist or two in, restring your bow and check the brace height. May take a time or two, and possibly taking a twist back out, but eventually you'll get it where it needs to be.