بسم الله الرحمن الرحيم
In the above mentioned case, your salah will be valid, you need not worry. If the dropping of the lizard was dry and so was your hand and you pulled your hand as soon as it touched the dropping or it was the dropping of a small lizard which usually lives on the walls and ceiling of the house then your hand did not turn impure. In the first case, no impurity touched in your hand and in the second case the dropping of the lizard is not impure. And in case it was the dropping of big lizard which has running blood and they usually live in forests then since the dropping touched your hand might have been nominal i.e. less than the quantity of one coin which is probable; hence in such case also your salah became valid.
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.