If you qualify under the "one petty offense" exception, you have nothing to worry about.
Mr. Shusterman's (former INS Trial Attorney, 1976-82) response to your question is general in nature, as not all the facts are known to him. You should retain an attorney experienced in immigration law to review all the facts in your case in order to receive advice specific to your case. Mr. Shusterman's statement above does not create an attorney/client relationship.
There is a petty offense rule in immigration that may apply to your conviction. Consult with an immigration attorney to determine if it applies and whether you have additional options.
Please note that this response is for informational purposes only and does not create an attorney-client relationship.