slight chest pain at the side when flat pressing.

[Meso_z]

especially with flat bench, i feel the part where my left pec and delt ties, a bit painful.

Now ive cut the flat benching and do flat dumbells instead, well the pain is much much better now.

Should i be careful to avoid a "possible" pec tear?

[jpm101]

Yes. Good Luck.

[YoungBlood]

I occasionally feel something similar, and I'm always careful when using either BB's or DB's. I prefer DB's however, since I feel that Chick does have a point in that 99% of guys that tear their pectorals is due to using BB's too much.
When was the last time you took time off? That's also a big factor as well. Make sure you stretch, and unless your lower chest is lagging & you're trying to bring it up, I would do BB's after you do inclines and/or flyes.