Biggie Smalls was shot and killed 15 years ago today ... but the rapper's female protege Lil' Kim tells TMZ ... she's still in mourning ... explaining, "It still hurts very much."
Kim -- who was famously close with Biggie -- tells us she'll be honoring his memory at a private dinner in NY with close friends and family members ... saying, "I will never forget him and I will think about him every day until I die."
She adds, "I will celebrate him every single day of my life ... I have endless love for him and I'll be grateful and thankful to him until my last day."
"I love him ... and will never stop loving him."
Biggie was shot and killed outside the Petersen Automotive Museum in Los Angeles on March 9, 1997. His killer has still not been found.