Hello, my husband has this but it's my understanding that he wont actually "recover" as such. I think its pretty near impossible not to get enough b12 in your diet since its in lots of things, I know in his case his body just cant convert it from food so he has injections instead and will always need them. Not sure if its the same for you though since you say you are on tablets so it might be different, maybe it depends on why you are deficient.
It doesn't really affect him at all, just when it gets close to when his top up injection is due he starts to feel really tired.
My marathon build up wont start for a few weeks, still focusing on 5k and 10k races over the summer. Have a half in the middle of August but am managing to maintain a run of about 15 miles once a week so I am not starting from too far back. Hoping for a sub 3.30 in Amsterdam.
I always run alone too apart from races, in fact I hate it if anyone asks if I fancy some company because actually the answer is always no thanks, I dont! Sometimes though I do cave in just so people don't think I am a totally unsociable cow.
I would suggest you see a physio as soon as you can and get it nipped in the bud. I had a really tight calf but it was actually tendinitis in the front of my leg which is why it hurt to flex. Often pain in one place is caused by an issue somewhere else, a physio can direct your rolling and icing more accurately. Once you know what you are dealing with rather than guessing you can rethink your plan and see where that leaves you