넘어졌어.

A: Check out this bruise. Pretty nasty, don’t you think?
B: It hurts me, just looking at it. What did you do?
A: 넘어졌어, on the stairs going to my apartment.
B: You’d better get some ice on that right away.

A: 이 멍든 것 좀 봐봐. 끔찍하지, 그치?
B: 보기만 해도 내가 다 아프다. 왜 그랬어?
A: I took a spill 아파트 계단에서.
B: 당장 얼음 찜질을 하는 게 좋겠다.

[Additional expressions]
*Check out this bruise.
– Take a look at my bruise. / Get a good look at how I bruised myself.
*Pretty nasty.
– It’s a bad one. / Pretty bad. / Kind of ugly. / Looks pretty serious.
*Don’t you think?
– Wouldn’t you agree? / Isn’t it? / Wouldn’t you say so?
*It hurts me, just looking at it.
– Simply seeing it gives me pain. / Only the sight of it looks so painful.
*What did you do?
– How did that happen? / What happened to cause that? / What went on?
*I took a spill on the stairs.
– I fell down some stairs. / I tripped and took a tumble down the stairs.
*going to my apartment
– leading up to where I live / that lead into where I’m living
*You’d better get some ice on that.
– You should put ice directly on it. / That ought to be iced up.
*right away
– immediately / without delay / Straight away / at once