Bruise like ball on my dogs left tummy

Hello! I have a 6 week old (May 1) shih tzu and I am worried. I noticed some ball thing in her left tummy when pressed lightly. She has a big tummy too and She eats very well and fast but seldom drinks water. Now She has a runny nose and coughs sometimes.

Hello!  I can't see clearly on this picture, but there is a massive range of possibilities for what you describe, including an inguinal hernia (lump like, sticks out through the abdominal wall in front of the leg, sometimes moves in and out under the fingers), ascites (fluid on the abdomen - this one can be worrying), worms, a normal puppy tummy / far deposit, a superficial skin lump.... In any case, it's a great idea to get a new pup checked over by the vet and some vets might also do routine puppy checks for a reduced fee or free of charge (this might exclude cases where they find an abnormality).  It is also fairly easy for pups, whether or not an abnormality is present, to pick up upper respiratory viruses, which can have a mild or serious effect.  I'm not sure whether you are a breeder about to pass the pup on to a new home, or a new owner who has come into possession of a puppy at quite a young age, but either way it is important to satisfy yourself as to what is going on here, so a vet appointment would be an excellent idea.  Please do come back with any more questions, and / or let us know how this little one gets on.

A bruise is technically a bleed under the skin and if a skin bleed has come up in a ball (heamatoma), it is definitely worthwhile getting it checked in this area.  Looking at the picture I don't think that's what you're looking at, but it's hard to tell from here so I thought it was worth a mention.

Thank you for taking your time to read and answer my question. A friend of mine give her to me last May 28. My first time owning a small dog. Last week, she falls to a hip high bed of ours and cries for a minute or two, I hope it didn't cause a trauma to her tummy. I'll get back here after I see a vet. Again, Thank you!