I do long walks each day, well most days - and my Bg always go slightly higher if I test immediately upon my return home. I am warm/hot as after good exercise, but not sweating buckets, if you know what i mean. However, I will have a large glass of water and relax for 30 min and my Bg is right down to normal (for me) levels.
Could be the same for you?? Of course liver dumps etc could also be the cause, but unless you test a few times after a walk/exercise you will not know how your body reacts to the exercise.
As I said, my Bg tends to go up a bit but quickly settles down again, so these days I do not worry unduly about it, unless I get lightheaded etc.
Might be worth you checking your Bg after walks, just to see if this reading is "normal" for you?? I got surprised/a little scared the first couple of times I tested after exercise, but soon realised that this is how my body reacted, so this wold be "normal" for me. Hence I do walks at a good pace and swimming, but not heavy exercise as that sends my Bg sky high and the crashes down into hypo levels!! Far too much trouble to deal with, when a good walk is gentler on my Bg! LOL
Alice