Bruises from injections for ED

Dear Forum,

I seem to be doing something wrong recently with my injection technique. I have been turning black and blue on my penis shortly after injection.

I was advised from the beginning to press down firmly at the injection site for five minutes. This I continue to do although black bruises appear within hours.

Has anyone else experienced this and does anyone have any tips to try to prevent this from happening....

Kind Regards
Leigh