Judged for something I did aged 16 how can I stop this?

[wasntsuchasweetsixteen]

As a (v immature) 16 year old. I did something awful. Told a massive awful terrible lie and then many other small lies to keep up the first.
I shouldn’t have. Obviously I know now how wrong it was and that I hurt people (my them bf and some friends).

Not to defend myself but to give insight into why this happened I was as I said v immature, also suffering abuse at home (emotional) and have asd and I had issues with boundaries and the truth. Anyway it was awful and wrong.
I tried to move on and move away from all that and learnt a lesson. However I’ve heard from someone recently that a friend had spoken to her about me after seeing my name come up on fb and wanted to ‘warn’ her about me.
I’m ashamed of my past but I was 16. This was a long time ago (I’m 42 now) I don’t want to be judged by a teenage mistake forever. I don’t know what to do

You need to forgive yourself OP. Most of us have things we're ashamed of. I'm 51 now and the way I behaved as a teenager still makes me cringe now, but I realise that some of it was a direct consequence of my home life then.
The person 'warning' your friend about you is very unkind dragging it up after all these years. I can't see how it affected it like the lady who's sister pretended she was ill, that's a bit different, so it says more about her at 40-odd than you.

I'd never hold this against a new friend I'd understand how and why it happened.
Walk tall OP be proud you've carried this burden to long.
You come across really nice.