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.
“Peace is within oneself to be found in the same place as agitation and suffering. It is not found in a forest or on a hilltop, nor is it given by a teacher. Where you experience suffering, you can also find freedom from suffering. Trying to run away from suffering is actually to run toward it.” ― Ajahn Chah