Dark rashes on hands with blisters, should I be worried?

[peppermintframe]

Almost a month ago I got very sunburnt at the beach. The sunburn has since faded but I noticed something else happen around the same time. Dark red rash-like spots appeared on the top of my left hand. These don't quite look like sunburns, more like solid dark purple rashes. There are about four of them, all located around my left pinky knuckle and the size of zipper. They are uniquely shaped, spotty, and finely-bordered almost as if I selectively placed sunscreen and missed these spots. There is no discomfort involved. In fact, I don't even know they are there unless I look at them. I know they are not sunburns because of the shapes and the fact that the rest of my burns have been faded for weeks. Additionally, small blisters continue to form on these spots randomly. If these faded with my burns, I would not be worried. The fact that they continue to persist this long after the sun makes me wonder what is going on. Is this some sort of strange reaction to the sun exposure or some allergic reaction or something else? Thanks for the help.