Kings rewarded a person who performed a heroic deed, had a notable achievement, or held a prominent position in government by granting them a noble title. Because Sweden limited the growth of the noble class, only about two percent of Sweden's population were noblemen. There was not much division between upper and lower nobility.
Most noblemen did not emigrate, and few disowned family members for unacceptable behavior. Thus, most traditions of a noble ancestor being "erased" or "eliminated" from all records are unfounded.
If your research in the original records of Sweden indicates that your ancestor was a nobleman, there are additional records that will be helpful. Although some original records (such as the grant of nobility) still exist, you can adequately accomplish most nobility research in secondary sources. These include published or manuscript genealogies of noble families. Some important sources for Swedish nobility research are:
Sveriges ridderskap och adelskalender(Genealogy of the Swedish Nobility). Stockholm, Sweden: Bonniers, 1854. (FHL book 948.5 D55s.)
Anrep, Johan Gabriel. Svenska Adelns Ättartaflor (Genealogy of the Nobility of Sweden). Stockholm: Norstedt, 1858-1864. (FHL book 948.5 D5a, film 1124532). These volumes may also be viewed online by going to Wiki-Rötter
Elgenstierna, Gustaf. Den introducerade Svenska adelns ättartavlor: med tillägg och rättelser(Genealogy of the Introduced Nobility of Sweden). Stockholm, Sweden: P.A. Norstedt & Söners Förlag, 1925-1936. (FHL book 948.5 D5e; films 1440193-5.)
Leijonhufvud, Karl Karlsson. Svensk adelskalender(Genealogy of Swedish Nobility). Stockholm, Sweden: P.A. Norstedt, 1899-1906. (FHL book 948.5 D22ak; films 1440245-6.)
The Family History Library has many records of Swedish noble families. These records are listed in the catalog under:
SWEDEN - NOBILITY
SWEDEN, [COUNTY] - NOBILITY
SWEDEN, [COUNTY], [CITY] - NOBILITY