I have red, hard bumps on my legs that look like bug bites

I came back from Iowa two weeks ago to Calif, and the day afer my return, I noticed two or three red bites on my leg, and assumed mosquito or whatever. Then a few days later, there were twice as many, and then a week later 15, some of which had grown into very hard bumps and itched. The itching was not severe, and was ok using Lanocane, but they didn't seem to go away and still here after two weeks. They are concentrated mostly on the outsides of my legs, but a couple on one knee as well. Some now have white 'heads', but most have just remained hard and red and sore, and do not look like a rash, but individual bites or sores. They do now seem to be less hard and maybe shrinking, but still sore to the touch and I'm concerned at how long they have persisted.

I have never been allergic to anything and am a healthy 52 year old. Should I just wait longer to see if they go away? And do you know what they might be?