I'm not a SW nor ever have been but I did work in a job role within child protection/children's services which exposed me to multiple child protection meetings so I learned from that what it is that SW are looking for, and it's all to do with your having insight.
So, if you were saying to SS "Oh, he didn't mean it, he tickles me too roughly sometimes and won't stop when I ask him, but it's not his fault, he doesn't know his own strength" that would be a red flag to them, that you don't understand the seriousness of the situation.
But if you're talking to them and set out what happened, how you photographed it, sought medical attention including with the goal of getting it put on record, enabled contact with SS and tried to address the matter with your DP. Then that having had a fairly decent response from our DP following SW contact he'd become accusatory, didn't feel any responsibility etc, you followed through with existing plans to remove yourself from the property and take steps to prevent his access to you and your child at this time in order to protect the both of you.
The latter shows that you tried, you sought the right care, you followed through with intended actions, and most importantly, you get that this man is a danger and that reasoning with him and thinking he will have a lightbulb moment and realise the error of his ways isn't something that's going to happen. THAT is what they want to see.
And you appear to have gotten to that place in your mind pretty quickly actually - you have actually taken action. Now if you then slipped back and they found out that after Christmas/New Year you'd let him have unsupervised access to your DS - they would view that as quite the opposite, no insight. And for SS, no insight means no ability to protect and advocate for your child.
So as long as you keep going in the way that you're doing at the moment, I can't see that they'll have any huge issues with you but at least you'll have support, formal records of what actions you took and how you handled it and their notes will reflect that you appear to have a good understanding at how to safeguard your son.
That's all what matters to them - it's the parents who keep taking the guy back, don't move out or don't make him move out, say they won't give him unsupervised access and then give him unsupervised access that give them concerns because they indicate a person who doesn't really understand that, sadly, it's not a unique situation (it is to you OP, and it's new to you) but in terms of how these things develop, there's a pretty set pattern with men like this and some inevitable endings none of which anyone wants to think about. Typically, for a long time, women will think that if they only just word it right, if they only can just get the message across, that the man with have an epiphany and change his ways and all that time the child and the woman, remain at risk. For the record: he won't change, he'll never get it, he will always be a danger. I think you're beginning to understand that now and that's a massive achievement in its own right.
Just hang in there.