I've been on maternity leave so he hasn't seen her for months. She looked after DS from when he was 1 to 3. He's now almost 4.
But I randomly said 'don't worry' to him in her first language (that she used exclusively with him) and he said (with a lot of question-answer), 'That's what "Jane" said. She was very angry when I was at the park and said I had to come in now. She hit me with a blanket when I was at her house. I cried and tried to run away but I didn't know how and she found me and hit me again.'
I asked if there was anything else and he said when he was at the park she pinched him "super-sharp" and he cried but she pinched him more.
I asked why he didn't tell me before and he said "I just didn't."
I asked him if there was anything more and he told me she poked him with a needle in his eye 
I don't know what to do in this situation. Any experience or advice?