It is normal for penile size to differ significantly between the flaccid and erect states.
Flaccid size is influenced by temperature, stress, and circulation, while erect size is more consistent and dependent on erectile tissue expansion.
Medical treatments such as penis enlargement surgery may increase flaccid length and girth permanently, while penis fillers increase girth temporarily.
Related pages:
https://moorgateandrology.co.uk/penis-enlargement-surgery/
https://moorgateandrology.co.uk/penis-fillers/