Dreadful, I won't sugercoat it. So don't read past the gap I'll leave in my comment if you don't want to know, because it is graphic.
He was my first baby, and 10lb 14oz. I'll put some space here so you can whizz past if you don't want to read it.
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I ended up with a 3rd degree tear, infected stitches afterwards which impeded healing, and overgrown scar tissue which was painful. I wore the thickest sanitary towels I could find, constantly, for a year, as I needed the cushioning. I couldn't have sex because it hurt too much.
The 3rd degree tear also caused toilet issues and while I wasn't fecally incontinent (thankfully!) the damage meant I got very little warning and had to get to a toilet immediately or risk an accident when I needed to poo. I couldn't fully empty my bladder properly for a while either.
I had amazing NHS physiotherapy for those issues and my bladder recovered on its own. I was taught to go to the toilet for a wee, wait ten minutes, then wee again so my bladder could empty properly. It took longer for the sphincter muscles/nerves to recover, but they did. This was years ago so I can't remember exactly what treatment I had, but I vaguely remember some sort of electrical stimulation (this may have been a diagnostic test rather than treatment) and a lot of exercises, including using dilators to stretch out scar tissue.
The overgrown scar tissue was burned away with silver nitrate (the same stuff they put up your nose to cauterise a bad nosebleed) which improved it, but I ended up having the whole scar refashioned under general anaesthetic and it's like the injury never ever happened. I can feel a thin scar but everything looks, feels, and works normally.
That all sounds horrendous written down all at once, and it was hard, but I knew I was getting the right help for it all. In the grand scheme of things, it was only a year, and I coped.
I had a very inactive birth (epidural, had to have forceps) but my DS was SO large and it was completely unexpected. I think I had undiagnosed gestational diabetes which contributed to his size. The labour itself was fine, honestly. I mostly laboured at home, and I had an epidural in hospital so I didn't feel any of the injury when it happened.
I've since had another DS, via elective c-section (such a lovely, calm experience) as I was told they didn't recommend a vaginal birth due to the issues I'd had. He was breech and had to be delivered two weeks early, so it would have been a c-section anyway.
DS2 was 8lb 10oz, so still a good size, but honestly, I reckon I could have sneezed him out. 
I had gestational diabetes diagnosed fairly early into that pregnancy and kept excellent control of my blood sugar, so he was smaller than his brother.
I'm not having any more but if I was, I wouldn't be worried about a 9lb-er. I would also keep more active during labour and would probably forgo the epidural so I could labour in a position where gravity could help.