I have something similar... I have a vein growing on TOP of my big toe.... it still has blood in it, but closed off at the end. when I cut my toe nails I have to cut the vein and it gets very very messy, so I have to press on it for ages to seal it off again. I've had it for over 25 years when I was in the army and having to wear steel capped boots all the time. Around 10 years ago i dropped a huge log on my foot and it totally ripped the toenail off. I was relieved as I thought it would grow back normal, but it didn't. I have had oral meds and creams and nothing fix it. The doctor said he would do surgery to cut the nail off and the vein. I don't believe him as I know that when I dropped the log on my foot and it ripped the nail off, it grew back again. I don't know what to do about it. It is embarrassing and I do all sorts of trick work with nail polish and fillers to hide it.
I know this is an old post, but I would see the podiatrist and have him/her remove the nail and have part biopsied, it is always best to err on the side of safety.