If you have gotten so many mosquito bites in your life that they no longer bother you, you have become inured to them. This means you have become accustomed to tolerating them.
This adjective is derived from the 16th-century phrase in ure, meaning “in use” or “in practice.” When you are inured to something, you have probably had a lot of persistent exposure to it, and it’s usually something negative. People can become inured to pain, inured to violence, and even inured to the sound of a little yappy dog that won’t stop barking.