Niall Horan Bleeding, Fan Throws Object Onstage & Injures One Direction Crooner After Knee Surgery! [WATCH]: Tweets 'Not Complaining But In A Lot Of Pain' [PHOTOS]

During a One Direction concert in Amsterdam on Wednesday (June 25), an overzealous fan threw a mysterious object onstage, and managed to hit singer Niall Horan right in the leg! Bad news, considering the "Story Of My Life" superstar just had major surgery on his knee a few months ago!

Fans felt really bad for 20-year-old Horan. After getting slammed with the object he sucked it up and continued playing, but looked to be in so much pain!

One concert-goer posted this viral Vine video:

After finishing-up the song, Horan clearly had trouble walking off stage. According to Gossip Cop, the popular boy bander was even bleeding due to the injury:

Fellow bandmates even tried comforting him:

(Twitter)

The gig ended shortly afterwards. Horan later tweeted:

@NiallOfficial: "Amsterdam thank you for a great couple of shows! Appreciate you coming."

@NiallOfficial: "Also guys! Can you limit what gets thrown on stage please! Coz somethin thrown at me tonight! Hit my knee! A lot of pain from it!"

@NiallOfficial: "Never wana sound like I'm complaining! But only having my operation 5 months ago, I still get a bit of pain and I'm very scared about it."

How polite! Looks like Horan will be okay - but still not cool!