Meaning of this sentence?

下がりに入ってから足の指が痛い

"If I step down, my toes hurt?" Guy was climbing/hiking down a mountain, and seems to have problem with his shoes. Or "Since we started going down, my toes hurt"?
Someone I asked said "My toe is sore from being on the slanted down [rocks]" which doesn't feel right to me...

Thanks in advance!

From the context you have provided, it's natural to assume that it means, as you mentioned, "Since we started going down, my toes hurt" in the sense that it's "Ever since we started going down, my toes (or it could be just one toe) have been aching".

Someone I asked said "My toe is sore from being on the slanted down [rocks]"

Well, it could imply that, because the toe(s) seemed to have started hurting ever since the hiker started on "the slanted down". But the toe(s) could have been sore before that, so it's too much to say "from being".