I havent the same problem, but it doesnt look to me like "chest pain" but more like "abs pain".
DOnt know if abs got tendons attouching them to the bones at the chest and u got a problem here, propably its not this.
It can be then i guess muscle pain on this specific area, propably from pushing too hard ur core/abs muscles? i guess it can also be nerve pain but i also dunno if thats the case...
My suggestion would be to easy back ur FL training, if u can do some progressions without having pain then ok , but if u do then i guess u must stop and w8 to recover.
U can try to stretch this area regularly maybe it helps.
Dunno if i helped even a bit, its propably isnt anything serious but u must be careful and if pain insist maybe u ll need to check on doctor especially if u have no clues what its about.
Goals: Be able to do bar-barians requirements in less than 10 mins, 10 good form one hand push ups, 15 pistols, Be able to do one hand holds on bar and controlled negatives, 1 min hanging l-sit, backlever hold for 5+ secs, advanced tucked FL for 5+ secs, advanced tucked planche for 8+secs etc etc
Long Goal (till summer): My 1st OAC,good BL hold, FL hold, bent arm planche, free handstand push ups, l-sit to handstand on handles, v-sit hold on floor