If you practised correctly then it's possible that this sensation was always there but up until then your mind was blocking it out or not sensitive enough to pick it up.
It's pretty normally to feel a lot more tingling and/or itching throughout the body as a result of this practise, though what you've described sounds a bit different.
If it's too strong for you to cope with then maybe a visit to the doctor is in order, but I'd recommend making this sensation the object of your awareness, see what you can learn from it, see if it's changing, observe the minds reaction ie use it as an opportunity.
"Whenever we feel that we are definitely right, so much so that we refuse to open up to anything or anybody else, right there we are wrong. It becomes wrong view. When suffering arises, where does it arise from? The cause is wrong view, the fruit of that being suffering. If it was right view it wouldn't cause suffering." - Ajahn Chah
"Remember you dont meditate to get anything, but to get rid of things. We do it, not with desire, but with letting go. If you want anything, you wont find it." - Ajahn Chah