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.
"Right effort is effort with wisdom. Because where there is wisdom, there is interest. The desire to know something is wisdom at work. Being mindful is not difficult. But it’s difficult to be continuously aware. For that you need right effort. But it does not require a great deal of energy. It’s relaxed perseverance in reminding yourself to be aware. When you are aware, wisdom unfolds naturally, and there is still more interest." - Sayadaw U Tejaniya