Thanks everyone for the concern. I’m fairly confident that it’s broke based on the pain and swelling, but knowing there isn't much they'll do I've strapped it up.
I have a fairly high pain threshold (walked on a broken foot before and separately with a broken patella amongst others), so the discomfort suggest it's damaged.
My own fault really - wasn't paying attention and kicked the bottom of the French door's frame full force without any shoes on. Under the nail is all bloodied.
I'm going to have a Guinness and a brandy before bed to hopefully support the feeling of comfort.