The European championship bronze medallist was accidentally hit in the face by Polish athlete Zaneta Glanc, who had mimed a throw while holding the discus, as she sat in the athletes' area next to the discus circle at Moscow's Luzhniki stadium.
"Coach asked me not to compete... but I had to throw to show my husband and parents watching on TV in Donetsk that I'm alive, feeling good and I'm the Iron Lady as usual," Semenova, who finished bottom of her qualifying group after managing only one legal throw, said in a statement released by the Ukrainian team.
"I'm so sorry it happened to me today as I was in great shape and showed strong results in practice. I was sure I'd throw in the final."
Semenova needed two stitches in a nasty-looking nose and will have to wait for five days until the swelling has gone down to find out whether she requires surgery, the statement said.
Immediately after the incident, Semenova was patched up by officials under the blazing morning sun in the competition area.
The 31-year-old, sporting a dressing on the bridge of her nose, continued with qualifying but managed only 55.79 metres, well down on her season's best of 61.41, and short of the automatic qualifying mark of 63 metres needed to guarantee a place in the final.
Pole Glanc did qualify for Sunday's final (1615 GMT)
"I was next to her. The Polish athlete was warming up and hit her in the face," Olympic champion Sandra Perkovic told Reuters.
"Her nose is broken. When I saw it, I ran over to help her. I took my towel to her and some water," added the Croatian who is favourite to take her first world title.
After coming off the field, a clearly upset Semenova walked past waiting reporters holding a bloodied towel to her nose, pausing briefly only to say she was going for medical treatment.
(Editing by Mitch Phillips)
