Most bites from insects will cause a white bump, as they inject poison in their sting. The hole in the middle can be puncture wound, or due to scratching the affected area. A good way to heal, is either bag balm which is a medicated petrolum jelly, or a combination of witch hazel, which will contract blood vessels and reduce swelling. The white is just white blood cells rushing to the infected area, and usually will clear on its own in no time, unless of course, a very venemous bite by things like black widow spiders or also an allergic reaction. There are many sticks you can buy which reduce swelling and itching, just check with your pharmacist and they can direct you if you choose to buy a more expensive product