I am running my very first 1/2 next Saturday (Country Music 1/2). Last weekend on my 10 mile run I found I had a blood blister under a callus on my big toe on my left foot. I did not pop it and it seemed to go down -- just the blood remained under the callus (it wasn't a blister anymore). I ran 7 today and the blood blister came back a little. I used moleskin but it's just slightly tender to the touch now.
I just can't decide if I should try and remove part of the callus or if that will just lead to more soreness.
I would leave it alone. It doesn't sound like it's bothering you much and it would just complicate matters trying to remove it. If the callus was likely to come off easily, the moleskin would have done it. Keep it padded and you should be OK.