Was the activity reported on Schedule C?
Or was the practice organized as an entity (if so, what type)?
Was the LLC taxed as a partnership or as a corporation?
Did you get a Schedule K-1?
If so, does the K-1 not reflect the sale?
If so, does the K-1 not reflect the different amount specifically allocated for sale of the goodwill?
It does not appear proper to me, from the limited facts presented, for you to report the sale of a business (or assets of that business) that was incorporated "outside the LLC/S Corp".
If the goodwill (or anything else that was sold) was an asset of the corporation, the sale would need to be reported by the corporation (and reflected on your K-1).
Or, before you personally can sell such an asset it would have to be distributed to you by the corporation and that distribution would have to be reflected on the corporate books, tax return and on a Schedule K-1 to you.
Of course, application of the general tax rules to specific circumstances does require all of the facts in order to make correct application and I may not be aware of all of the facts in your case.
You may wish to consult with the attorney and tax practitioner that assisted you with the sale to confirm how the sale was structured.
I will opt out of this question to allow others an opportunity to answer.