This is called “die swell.” It is caused by pressure inside the nozzle, and is primarily an indicator that the filament is being over-extruded for it’s current parameters (too much, too fast, too cold, or any combination thereof). All filaments have a certain degree of die swell, and usually it is unnoticeable, but some have more than others (clearly). It is nothing to worry about during the loading process, but it is one of the reasons you need to tune your printer and slicer settings for each individual filament when printing with it. With proper tuning, this won’t be a problem. The best process for print tuning can be found here, at the bottom of the first post:
Also, keep in mind that silk PLA filaments are more prone to moisture absorption than regular PLA, so you need to make sure it has been dried (one of the listed steps in the print tuning).