What kind of oil is it? Do you keep it in the fridge, or is it cool where you live? I ask, because I get the same thing with my rice bran oil, avocado oil and olive oil when they are stored at cooler temps. If that's the case, no worries- it's just the sturdier acids such in them such as palmitic and/or stearic acid solidifying at the cooler temps. They always start solidifying from the bottom up.