Wonder Why?

i skipped gym totally last week. apart from a walk i did on tuesday which *was not that far*, i pretty much didn't do anything. but how come my legs are wobbly, my muscles are sore and some discomfort in my left hip flexor. i did those hip rotations exercise i learnt during pilates and it only helps a bit. my body should've feel great from not doing any streneous thing yet it feels like this. age catching up? hmm ..