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.
"Proper effort is not the effort to make something particular happen. It is the effort to be aware and awake each moment." - Ajahn Chah
"When we see beyond self, we no longer cling to happiness. When we stop clinging, we can begin to be happy." - Ajahn Chah
"Know and watch your heart. It’s pure but emotions come to colour it." — Ajahn Chah