Hello, well first of all my sympathies, we poor mums always seem to feel guilty about something. Remember that saying 'a mother's place is in the wrong' ? I'm still feeling like that some of the time 'did I do this right, would it all have been different if I'd only...' and my DDs are much bigger than your LO
The truth is that they mostly survive and thrive whatever choices we make, and that nursery is a positive experience for most children, but at 2.4 I do think he'll find separation a little strange at first, especially if he's been with just you up till now. You don't say how many days/hours he will be doing?
I used to co-run a nursery/playgroup and it's certainly true that SOME children do settle easier if parents never stay with them from the start. It is often said, and really true, that some cry heartfelt tears until mum's disappeared down the path - and then settle for a happy morning - though poor mum has gone off feeling terrible and worries the entire time. A sympathetic nursery will be able to help your DS through these early days and will/should contact you if he ever did become really upset, so you should be able to leave him without undue worry that he will be in terrible distress for any length of time.
Since he's only 2.4 I'd be a little torn though and maybe it might be a good idea to stay with him until he at least knows the setting and hopefully has built up some trust and friendship with the carers there to attach himself to in your absence.
Both of my own DDs were very clingy and one thing I did was be very firm (however much I was breaking up inside) and make it all seem absolutely normal and good - I'd say 'no, mummy can't stay, mummies don't go to nursery, look, you can see the others don't have mummies here. I will go off to do some shopping for a little while and then be back to get you when you've had some fun playing and all the mummies come. Would you like me to buy a [small treat] at the shops for you to have when I get back?'
Good luck and try not to worry, it's difficult for everyone the first time we send our precious little one off without us, but the fact is, most do (and must) take it in their stride if it's all sympathetically handled by the nursery staff. And you may be lucky and yours will be one of those who strolls in without a care in the world!