I'm on my second playthrough of skyrim and have recently started with a new imperial male. Since I've played before I know quite a lot of locations around the map and ended up on ancient's ascent yesterday (where there's a word wall)

Now I've not reached the point where I've fought my first dragon and absorbed its soul so there is of course no dragon there and I thought the wall would be inactive. But imagine my surprise when I absorbed the word on the wall as I approached it. Now I know my first ever word in the game.

So just wondering if this is normal and won't bug my game and progress. I of course cannot activate the word until after dragon rising, which is quite further up my main quest line.

Nope, it won't. You just can't do anything with it until you unlock it.