I did a 40 mile event in torrential rain & mud (ie Probably the equivalent of >40 miles) last year and, only in hindsight mind, had my left boot done up a bit too tight. Old, well broken-in boots.
I suspected shinsplints too, which I’d had before due to “too much too soon” running.
This was different though – noticeably due to the red marks, burning sensation and pins/needles. The pins/needles could even be set off by touching the top of my foot – like they were linked.
It transpired that it is not uncommon and was caused by, effectively, trapping tissue/nerves and starving them of blood/oxygen. In extremis you kill the tissue.
Can’t remember what it is called. Will have a dig back through some old stuff.
It is still not *right*. Though I’m running 50-60 miles/month again, the pins/needles sensation is still there to a lesser extent.
Rest. Rest. Ice (I had to buy bags and submerge my whole lower leg in a bucket. ow! Ow! OWW!). More rest.
Good luck.
In my case, the boot upper caused much of the trouble.
I’m doing the same event in three weeks actually – and wearing trail shoes this time 🙂