Our toddlers behaviour is a real concern.

[Legionoffools]

Hey guys, we have a beautiful daughter of 2 and almost 3/4. And she just basically doesn't want to play with other little ones her age. In every social situation she becomes massively shy: holding on when hugging, her face into the shoulder, refusing to be put down.

She's also seemingly really unhappy at her nursery, she seems to cry an awful lot. I drop her and Mum outside the nursery and every time she seems to be really upset. The nursery has an awesome rating in that government ratings thing, but she seems to not enjoy her time there at all. Nurseries are maybe prisons for the innocent.

I'm sorry I'm waffling, the nurseries and prisons thing was pseudo-funny conjecture.

Anyway, she has HUGE separation anxiety with her mum and I: Sometimes when I take our dog out for a walk, she has a massive meltdown, I reassure her etc, and sometimes walk the dog after bath time.

Shes just so stoic and outgoing when she's with people she knows, big or small. But an unknown situation, even with toddler friends that she knows, she clams up, like I said.

tl;dr version:
You hit this before reading my words. Shame on you.

I took it to be gender awareness not sexual, and didn't see any problems in the comment.

I looked after a little girl. She was petrified of any adult man from about 10 months until about 18 months, except her dad, who she loved. The only other adult male she saw frequently was her grandad, who she would watch and smile at from behind her hands.
If a male old enough to be seen as an adult even smiled at her she would cry, if they spoke to her she really got upset.
Her mum was worried, and asked the HV who said that one of hers had been the same, and it was quite common.
She grew out of it naturally without any intervention, and there was nothing that started it off as far as they noticed.

I remember a conversation with my aunt. Her dd age about 2yo at the time, was a real chatterbox and would chat to anyone. She'd started calling all men "aunty" and all women "uncle". Never worked out why she chose that way round but she was totally consistant.

So they can be aware of gender, and react to it.

On the shyness. My dd2 was so shy until she was about 2.6yo. Clingy, wouldn't look at another child. Dd1 was confident and was playing with other children, and wanting to be with other children at that age.
Dd1 (age 11 now) is much more shy than dd2 (age 8yo) and it has been the case since each of them was about 4yo.

My ds has a real problem with men. Only my dad and DH get a look in!