Uncomfortable glasses are a nightmare and we cannot sympathise enough with symptoms such as pinching on the ears/nose pads, and even headaches in more acute cases. The main reasons for these symptoms are either an incorrect lens power, which usually results in headaches, or the frames not being tailored appropriately to fit your face, which results in the pinching.
You should not despair as adjustments may be necessary when you buy new glasses. We would recommend returning to your optician explaining your experience with your new glasses, as it may take a few sessions of trial and error. It is not advised to attempt to adjust them yourself.
If these symptoms don't match your troubles, we may also suggest investing in some high-quality frames with lens treatments such as anti-glare/anti-reflective. These can be useful if you are experiencing ongoing headaches, work for long hours at a computer or are regularly exposed to bright light. If the problem persists, you can ask for your prescription to be measured again, as this is an unlikely but not impossible reason for feeling uncomfortable with your glasses.