No worries.
You could copy some to an SD card to save some space. However, it is recommended that you have an external hard drive to keep a Time machine or other backup of your data. If your internal drive is filling up, it may be best to get an external to move your Photos Library to, then use a second to backup the internal and that external to. All drive types will fail at some point, and removable flash storage drives can somewhat be more susceptible.
Also, depending on your setup, you may try using
iCloud Photos as a way to free up some storage space.
C