Yep had complete ACL tear. Took me 18 months to get back in to football, but I was back MTBing within 10 months. Probably not the timescale you were wanting to hear.
MRI def push for. A&E just took an x-ray which would not show damage and even the Dr missed the damage. Apparently they do a kind of knee click test!
Just ice up and rest if it is swollen?
I’d avoid the bike until you know for sure. I just had some ankle weights and just did some knee exercises, but a little at a time. best thing I did was go and see a physio, they gave me a contraption that strapped around my knee and a pipe led in to a barrel that contained ice and water. Worked wonders as you could have it on longer than an ice pack.
so. Book GP and book a private physio in the mean time.
Heal up soon