Thanks Bruno,

It's the bottom portion of "Ischium" from the image that touches the ground when sitting. You see where the bottom of it is kind of pointy?
It feels like that spot is sticking out of my buttock when I'm on the cushion. So I increased the walking meditation. For now it's: one hour of sitting, half an hour of walking. I also go out and walk around my neighborhood whenever I can.
And nowadays, I start my meditation with Metta Bhava - loving kindness. But if I'm agitated for whatever reason, I proceed straight to insight meditation without doing metta. I can't seem to arouse compassion when I'm overwhelmed with negative emotions. But when I can properly practice metta, I can feel the energy of compassion from wishing well for others arising and it kind of feels like a very minor rapture. It's too early to determine if this metta practice is really helping with my pain at this point but I am going to continue with it for now. I am fairly new to this metta stuff so I'm still trying to get a good grip on the technique.

Today as I was meditating, the same pain arose again. I noted it and it either subsided or kind of faded away. From that point on I decided to treat this new pain as I have done with my other physical pains (although not as severe as this one) during the retreats in the past:
Note, note and note!!!!!
I guess there's no other alternatives but to put up with it. Stop practicing altogether just doesn't seem like an option to me. I will see how things pan out in next few weeks.
I do want to go on an intensive retreat (3-4 weeks) but am not sure if I can at this point.
Anyway, thanks again for your reply.