The 28-year-old centre, who returned home last night with his leg in plaster, received confirmation of the break on Saturday and will have a pin inserted in his lower right leg.
The injury will keep Tindall, capped 53 times, out for 12 weeks but England will hope he will be fit to return for their World Cup defence.
He will also miss Gloucester's Premiership title run-in and England's Test match appointments with the Springboks in Bloemfontein (May 26) and Pretoria (June 2).
Recalling the accidental clash, Flood said: "I stepped one way and I think Mike instinctively stepped the other, then I felt his shin hit my thigh really hard.
"It was just one of those things nobody can do anything about, but I feel desperately sorry for Mike because he is a nice bloke and a great player.
"It is deeply upsetting to see anybody seriously injured, and I just wish him all the best."
Tindall, a World Cup winner in 2003, started four RBS 6 Nations Championship games this season and is a key part of England head coach Brian Ashton's planning.
Injury-plagued Jonny Wilkinson also failed to last the distance last night, going off with a rib cartilage problem in the same game.
Flood added: "It is obviously disappointing to see Jonny go off in any game, but to be fair he just took a whack in the ribs and he was fine down in the changing room after the match.
"Obviously, he is a bit sore, but it doesn't seem too serious, thankfully."