I just started my pre-training for my 18x enlistment and did my first ruck today. I went on a 4 mile ruck over some pretty rough terrain that contained sand, rock and grass at different points plus some hills (im in Florida, hills are hard to come by

) I completed this in about an hour and 10 minutes with 30lb pack. I recently bought some Altama jungle boots as well and this was their first time out. Before the ruck march I treated them over night (twice actually) with mink oil and I also prepared my feet with arid XXX and foot powder right before I went out. At the end I felt pumped out knowing I was on my way to attaining my goal and logging my first miles. My dilemma is that I did attain 1 blister (dime sized) on my left heel. I dunno if maybe I bought the wrong size boots (which then im screwed since altama doesnt take returns after use) or am I gonna attain blisters no matter what I do to prevent them. Looking for the BTDT thoughts... Should I just suck it up and keep rucking or revaluate what Im doing?
p.s. I made sure I was using army issue socks. (Believe all my t's are crossed and i's dotted). Also thanks to the professionals on this forum and Warrior mentor for all the valuable info made available.