You definitely need to get an alignment. As I recently learned, when you lower a car you change the camber and toe. I didn't know this when I lowered my car right after I bought it, as it was the first time I had a lowered car. It cost me a set of tires, but lesson learned
Also, in order to align it properly, you will need an adjustable camber kit. I found that out after my first alignment couldn't get it within spec.