Dull Pain

[someone444]

Dull Pain...Probably Xiphoid Process?
I didn't knew where to post this (in which category), so I did here. I hope it's ok.

First of all, I'm a smoker though, just to mention so you can give me more accurate answers and help me about it.

I have dull pain down in the middle of my ribs below my breastbone...It has started a few days ago, and I've noticed when I don't smoke a day or two, the pain slowly goes away. Yesterday I've been on a party and I was drunk (drinked some hard alcoholic drink, it contained 40% of alcohol, just to mention it as well), so I've smoked around 13 cigarettes through the night.

I'm smoking since around January 2011. (So ~1 year).
I also had a lung collapsion (Pneumothorax) back in late 2008. I know, it's very bad to smoke for me (for everyone, ofcourse..but for me especially), so I'm definitely stopping with smoking. I've been already in the progress of stopping since more than a week.

Now a little description about the pain (How it feels):
- It is dull, and constant. The pain starts right from the end of breastbone and goes down till the end of that "thing" what I'm talking about (what hurts). Guess it's the xiphoid process, but not sure. It's that are where xiphoid process is.
- What affects the pain:
*When I breathe in as deep as I can, the pain becomes (just a little) more intensive.
*When I touch it, and press it a little, the pain doesn't get worse, even I feel like it hurts less then.
*Sometimes (not always) there's some extra pain...sharp and short (for a short time)...that extra pain occurs in the same area where the dull (constant) pain is, and it came yesterday 2-3 times and today as well. just randomly...

How my middle of my ribs looks visually:
- On one side it looks like it's a lil' more out, while on the other one is normal. The whole area around the Xiphoid Process is flat and tough...It's like it's a little more out than it should be...I don't remembed I was able to touch it just like now...now it's more out...Nothing more I'd say...

I really hope it is not a big problem...Like cancer or tumor or stuff like that...
So:
- What is it?
- What should I do?

Thank you very much in advance for your help!

BTW: I'm 19, male.