League strugglers Lecce deny Lazio
Francesco Matuzalem put the home side ahead in the 82nd minute after both teams had previously been denied by the crossbar.
Bojinov then came to the visitors' rescue by scoring the equaliser seconds from time.
The result kept Lazio in third place and holding the last Champions League qualifying spot with five games still to play in Serie A.
Lecce remain in 18th position, one point behind Genoa and safety.
The visitors went into the encounter at the Stadio Olimpico knowing victory could see them climb out of the relegation zone for the first time this year.
They enjoyed a strong start and could have gone in front in the 13th minute when Juan Guillermo Cuadrado fed David Di Michele in the left side of the area and his 10-yard effort went wide.
Antonio Candreva was unlucky not to give the hosts the lead midway through the first half when his cross-shot surprised Lecce goalkeeper Massimiliano Benassi but struck the woodwork.
Lazio then wasted a great chance before half-time.
Benassi could not hold on to Tommaso Rocchi's goal-bound attempt and Candreva missed an open goal when he fired wide.
Lecce almost went in front seven minutes into the second half when Cuadrado's right-footed volley from Guillermo Giacomazzi's corner beat Lazio goalkeeper Federico Marchetti but struck the bar.
Instead Lazio broke the deadlock when Matuzalem got his head to Lionel Scaloni's perfect cross and his powerful effort beat Benassi. Lecce pushed forward in search of the equaliser and were rewarded.
Lazio failed to clear the ball in the area and Bojinov, who had come on just three minutes earlier, struck from 12 yards past Marchetti to stun the home fans.