Is there an alternative pre-school Badvoc? Is this a 3 year-old nursery place? (Sorry confused as pre-school round here is for 2 year olds, then they go to nursery at 3.)
Nowhere near the same, but dd has been bitten twice this week by the same girl at her nursery. Once outside before we went in and then again during the session. The girl concerned is the same one that used to beeline dd at every toddler group and take toys off her, push her etc. Dd is very good at sharing and doesn't really understand that others might not be so kind, so never stands up for herself or ask for help from the teachers.
I went to see the teacher before nursery yesterday and told her that, whilst I understand these things happen with children sometimes, I wanted her to be aware that it had happened outside, as well as inside nursery and is therefore less likely to have been 'accidental' as the other girl claimed. Imo the relationship between the two needs careful monitoring. She was fine about it, listened to and understood my concerns and said she would keep an eye on the situation - she is an excellent teacher and I trust her to keep to her word. Dd came home yesterday and said they had played a nice game together 'with the teacher' and the other girl was kind, so I think the relationship is now being 'handled'.
There's no way the manager should be ignoring your concerns. I would expect that at the very least they would keep a close eye on the two children and observe their relationship before making their minds up.
That said, we have three boys who have suddenly decided they don't like nursery anymore. All three were screaming the place down when I dropped dd today. 
However, I happen to know the teacher very well, as her dd was born just after mine and her ds is in ds2's class. She is absolutely lovely and amazing with children, same for the HLTA that's also with that nursery group, who had both my boys and they adored her. The boys are just exhausted after a few weeks of going every day, they've had to drop their naps and they are just starting to realise that they have to go every single day. In my experience, boys are often more likely to want to cosy up with Mum at home than go to nursery and some days that's all they want and nothing will persuade them otherwise.
I would say though, that if you are really concerned and your ds is that unhappy then you are best placed to judge whether it's the latter or down to something that's going on at nursery. If you don't have confidence in the staff to listen to your concerns, take them seriously and act on them, then could you perhaps try a different pre-school or even just pull him out until he's a bit older. Not all children are ready for full-on nursery day-in day-out at this age, some do much better if they wait a year and are just that bit older and more able to cope.
Sorry you and your ds are going through this. Ds1 was bullied right through the infants and the start of the Juniors and I know how heartbreaking it is. At this age the staff should be on-top of and handling any sign of intimidating or bullying-type behaviour and actively working with the children to develop and reward appropriate behaviour and relationships.