If you got sparks from a 12V line, then whatever that 12V line was attached or fused to is where the problem is likely to happen. It's unlikely that the positive for the cigarette lighter is going to be an issue, unless you grounded that.
The other 12V line, is that something that you added yourself? If it's a factory +12V line, then you need to check the fuse for that.
If it's from the radio, many times, an aftermarket radio will have its own in-line fuse on the constant and switched power. Check those, as they're often smaller than the factory radio fuse (Though not always.)