If you happened to be sat near the overwing exits, it's a common phenomenon. Well actually it's just plastic stretching against plastic. The overwing exit cabin side wall feature doesn't fit vey well with the main plastic sidewall. So as differential pressure increases with climbing, do the 'plug' gets more snug, and rubs and creaks as it does so. A clicking sound can sometimes also be heard.
All quiet common. The odd thing is sometimes you notice it, sometimes you don't. I'm sure there is a logic to it somewhere.