Dojo,
I see this is your first post. Welcome to the forum. Here’s a brief review:
• see your physician
• learn pranayama from a highly skiller teacher
These are two primary principles and I only have a couple of things to add to an already sound foundation.
As Nichole eludes to above, the way in which a Poster presents themselves, especially in a situation of concern, safety, injury, or illness, has to paint a verbal picture of you as a person. Your age, gender, fitness background and any pertinent conditions or medications you are into would be very helpful.
Since we do not know what sort of “deep breathing” you are doing, where you are doing it in the anatomical body, and for how long and in what way(s), we can’t speak much to it. If you want precise feedback on that I am certain we are all willing to craft such a thing; with more details from you.
The chances of you doing one session of this “deep breathing” and having an issue from it that requires a physician is a bit unlikely. It is not, however, impossible - again, depending on what you were doing.
What is more likely is that you were, in this breathing, moving muscles that surround the home of the breath: the rib cage. If you are not used to moving the rib cage (read: shallow breathing and no yoga) then the muscles and tissue et al around the rib cage can certainly hurt, and quite a bit at that. Usually this is a day or two after the event in question.
NONE of this means “forego the doctor”. It is always better to err on the side of caution. But I would be very, very surprised if you had done damage unless you’ve been doing this over some months undirected.
