Blackened / Bruised Right Little Toe Nail

portlanders

Been running for 18 months or so in NB Zante V3's (currently rotating old/new pairs), not greatly increased running distance or frequency (i'm in week 5 of 16 week marathon training), had to change socks as More Miles no longer sell ESAA ones in my size, so changed to More Miles London.

I occasionally run in a trail shoe for parkruns, but only maybe twice a month - and shoe does rub on top of toe adjacent to small toe but on left foot. Last run in these Friday last week in the snow. 

But now i have a blackened toe nail, little toe on my right foot. Not painful or swollen.

Just wondered what could be causing it, and how to remedy the situation so it doesn't get worse as in marathon training. 

Possible remedies I've thought of is -

• maybe laces too tight on new shoes so loosen them at the bottom.
• Stop wearing the parkrun shoes. - Think i'll do this anyhow as not enjoying parkrun.
• order some more miles Essa socks in the available next size up (i'm a 10/10.5, this size is for 11-13)

All other toes fine - little toe on left foot absolutely no problem.

Any ideas, and how should i treat the black nail, just leave it?

Thank you