Can fordyce spots become bigger or get inflamed?

Yes,: These are sebaceous glands. They do not have a hair follicle associated with them, so they are less likely to get swollen or infected like other sebaceous glands but the possibility still exists.

Not usually: No, these usually do not get infected. Just as much risk of infection of these as with regular skin infection, hair follicle infection etc. The also do not get larger.