If you just recently purchased this home you should know that seller's are required to test homes built before 1978 for lead paint. If lead paint is discovered the law requires that that information be passed to the prospective buyer.
There is no special lead preventing paint that I am aware of and painting over lead paint is not always the best solution. You should have a qualified tester come to your house to do a complete inspection. He or she should should be able to determine what type of action you should take. In the meantime clean your house throughly removing as much dust as you can and (I know it's hard) try to keep your child from touching the walls. Frequent hand washing is very important.
I have included this link so you can become better educated on the subject. I hope it helps.