I can't say for certain. It certainly could be a pimple, and cold sores (herpes) are usually a
clusterCluster headaches of blisters, not a single bump. For definitive diagnosis, you'll need to see a doctor when the bump is present (though a good quality photo might help.) If it's a cold sore, antiviral oral or topical medication may help. If it's a pimple, topical antibiotics may be useful. Neither is helped by squeezing. A doctor should be able to set you straight.
Best.
Dr. Rockoff