Although there is no specific context given for this example sentence (as you have said,) I wonder if the idea of this sentence could be something like:
(I will) spread (the cream or medicine?) on my foot/leg until (I get to) the next town.
in the case that, perhaps, the subject of the sentence was injured somewhere outdoors and had some cream or medicine to temporarily help the injury? Or perhaps the cream is sunscreen?
The overall meaning of this example sentence depends on the missing (or implied) information, though...
As the original example sentence ended up being a little different in reality than in the original question, I would look toward @marasai's answer. Maybe this answer (as it is now) could be an example of how much sentence meanings can potentially change when different particles are used...